This research proposal is concerned with the detailed structure of the M protein and its relationship to other components of influenza virus. This protein is the major structural component of the virus, constituting at least 40% of the total protein. Details of interaction with the lipid or other proteins is unknown. Data has been acquired which indicates the protein to have a high affinity for lipid, since it incorporates very readily into lipid vesicles formed in vitro. The protein inserts into the lipid vesicles by a fragment of about 5,000 daltons. The primary structure of this fragment as well as the whole M protein is being determined. Studies are also continuing with temperature sensitive mutants as these relate to aspect of replication and assembly of the virus.